1. Field of the Invention
This invention relates to a wide-field AF camera capable of setting a distance measuring area (focusing area) in a desired position in a photographing image plane and detecting the point of focus, and more particularly to a photoelectric converting device therefor.
2. Description of the Related Art
As an example of a conventional photoelectric converting device, a photoelectric converting device having a monitoring photo detector arranged near and in the same plane as a charge storage type image sensor to control the integral time of the image sensor is disclosed in U.S. Pat. No. 4,410,258.
When the area of an image sensor is enlarged to attain the wide-field distance measurement, the luminance distribution of wide dynamic range cannot be covered by use of only a single monitoring photo detector. Therefore, a method of dividing the image sensor into a plurality of blocks, providing monitoring photo detectors for the respective blocks and independently controlling the integral times thereof is considered. However, with this method, since a signal becomes discontinuous at the boundary portion between the blocks, the point of focus cannot be detected when a distance measuring area (focusing area) is set to lie over the two blocks.
The above problem is explained in more detail with reference to FIGS. 23A to 23D. FIGS. 23A to 23D show a case of wide-field line AF.
Assuming that four blocks of pixel groups (1), (2), (3) and (4) are provided as the focusing areas as shown in FIG. 23A, an actual light component shown in FIG. 23B is obtained. FIG. 23C shows an output obtained in a case where all of the focusing areas (1), (2), (3) and (4) are processed by use of the same integration controlling element. FIG. 23D shows an output obtained in a case where all of the focusing area blocks (1), (2), (3) and (4) are processed by use of respective integration controlling elements. When a main object lies in A or B, the dynamic range of the signal is determined by an amount of light of (4) which has no relation with the main object A or B in the case of FIG. 23C so that the precision of the point-of-focus detection will be lowered. In the case of FIG. 23D, since the light amounts in the focusing areas (1), (2), (3) and (4) are controlled to optimum values, there occurs no problem when the main object is B, but when the main object is A, since the light amounts in the focusing areas (1) and (2) are not continuous, the actual light distribution cannot be reproduced.